Field of the Invention
The present invention relates to a piezoelectric ceramic and a ceramic powder raw material for the piezoelectric ceramic and more particularly to a lead-free piezoelectric ceramic and a lead-free ceramic powder. The present invention also relates to a piezoelectric element, a multilayered piezoelectric element, a liquid discharge head, a liquid discharge apparatus, an ultrasonic motor, an optical apparatus, a vibratory apparatus, a dust removing device, an image pickup apparatus, and electronic equipment, each including the piezoelectric ceramic.
Description of the Related Art
In general, piezoelectric ceramics are ABO3 perovskite-type metal oxides, such as lead zirconate titanate (hereinafter referred to as “PZT”). However, PZT contains lead at an A site of its perovskite structure. Thus, the adverse effects of the lead component on the environment are regarded as problems. To address these problems, piezoelectric ceramics and piezoelectric elements that contain lead-free perovskite-type metal oxides have been proposed.
Known piezoelectric ceramics composed of lead-free perovskite-type metal oxides include barium titanate (BaTiO3) and its derivative materials. Journal of Alloys and Compounds, 2013, vol. 574, pp. 88-91 discloses a piezoelectric ceramic in which the A sites of barium titanate are partly replaced with calcium (Ca) and the B sites of the barium titanate are partly replaced with zirconium (Zr) in order to improve the room-temperature piezoelectric constant of the barium titanate. Furthermore, manganese (Mn) is added to improve the mechanical quality factor of the barium titanate.
Improvement in mechanical quality factor is effective in reducing the heat generation and power consumption of a piezoelectric element in operation. However, the piezoelectric ceramic disclosed in the journal has a still low mechanical quality factor. Although Mn may be further added to the barium titanate to further increase the mechanical quality factor, the amount of Mn is negatively correlated with the piezoelectric constant, as shown in Table 1 of the journal, and the addition of Mn results in a decrease in piezoelectric constant. Thus, satisfying both a high piezoelectric constant and a high mechanical quality factor is a challenging task.
The present invention provides a lead-free piezoelectric ceramic that has both a high piezoelectric constant and a high mechanical quality factor and a ceramic powder raw material for the lead-free piezoelectric ceramic. The present invention also provides a piezoelectric element, a multilayered piezoelectric element, a liquid discharge head, a liquid discharge apparatus, an ultrasonic motor, an optical apparatus, a vibratory apparatus, a dust removing device, an image pickup apparatus, and an electronic equipment, each including the piezoelectric ceramic.